Scientific objective: Spectral resolution of shock layer radiation. Resolve spectral lines of air plasma emissions at optical wavelengths for the measurement of excitation temperatures. Provide high spectral resolution and absolute calibration at high dynamic range. Limitation: only one measurement made in a brief time interval during the point of peak brightness.

Instrument validation tests: This camera has been used extensively in past missions. Laboratory check on spectral response.

Sensitivity: An 0.1 second exposure results in +10.6 magnitude stars being detected.

Dynamic range: 16-bit (factor 65,536).

Frame rate and exposure times: The camera has a 5 degree field of view and can measure the SRC emission over a 5 degree length of path. The SRC will move at a rate of about 0.88¼/second, accelerating, in azimuth. The exposure time is chosen such that integration on the star background is not dominating the image. Typical exposure times in past campaigns: 0.1-0.8 seconds. After each exposure, there will be a 1 seond read-out time (full frame, or less with binning, binning option 1x4 in spatial but not in spectral direction). Period covered: 49s until 55.7s, equivalenth to 63.5 to 57.6 km altitude range around the time of peak heating (and peak brightness). Number of spectra (time resolved): up to 100, each representing about 0.02 degree of motion on the sky.

Spectral resolution- gives the FWHM of an instrument-broadened unresolved atomic spectral line:In first order: 0.26 nm. Full wavelength range: 137 nm, centered on central wavelength depending on the angle between viewing direction and the SRC. Dispersion is 0.1338 nm/pixel. We anticipate aiming for 743-880 nm, centered on 811.5 nm, or 41 degree angle between viewing direction and SRC. The SRC will be at 12.1 degree elevation, needing the camera to be mounted at a 53.1 degree angle with respect to the horizon. The window is at a 62¼ angle.

Relative spectral response - gives the wavelength dependence of the combined system (window, lens, spectrograph, and CCD camera). The Quantum Efficiency of the system depends somewhat on the angle of viewing through the window (window absorption at the near-UV cut-off). Values need to be multiplied by cos(angle), with angle the viewing angle of the camera away from the position of the Sample Return Capsule: